In conching machines, whenever a chocolate mass or its recipe is changed, the conching machine has to be cleaned. In general, having finished a conching operation, the final chocolate, coating or the like is pumped off by means of a chocolate pump. After this, residues of the chocolate mass will remain at the inner wall surface of the conching machine and will adhere on the tools which, in general, are scraper, shearing and/or mixing tools. After pumping the finished chocolate mass off or permitting it to flow off, for example, within a conching machine of 6 ton volume about 25 kg of mass will remain in it and have to be removed. This is, because this fact proves to be interfering with changing the type of chocolate mass, particularly when switching over from a dark mass to a light-colored mass. In such cases, undesirable "blends" may occur, and colors may be carried over.
Heretofore, in order to clean the conching trough, an "intermediate mass" has been processed, thus performing rough cleaning. Subsequently, this "intermediate mass" was removed, and the conching trough was filled up with cocoa butter which was used for fine cleaning the trough.
Introduction of cocoa butter and of other substantially liquid substances, however, occurs also when conching a chocolate composition where an exact proportion of such a substance has to be added and homogenized within the mass which has already undergone a first or even a second conching step.
Usually, when fine cleaning a conching machine, the cocoa butter is emptied after running the conching shaft for a while. This procedure is both expensive with respect to energy consumption and requires also a large amount of cocoa butter which is expensive itself. It takes much time, and large amounts of "intermediate mass" will accrue and will have to be recycled in an appropriate manner. Alternatively, conching machines, i.e. the trough walls of them, are cleaned in a mechanical way, but expenditures are quite high.
For example, EP-A-0 526 771 discloses a conching machine whose covering lid is cleaned by means of scrapers. Such an arrangement is, however, not suitable for cleaning the inner wall surfaces of the conching trough.